When using a video output card (such as an HDMI card), where software control over parameters that contribute to the output video frame rate is available, and given that frames to be displayed are presented to the software along with accurate timestamps when they are to be presented through the HDMI output connector (this also applies also to other types of video display hardware such as DVI, VGA, Display Port etc.), a method is needed that will control these exposed controlling parameters, minimizing the error between the desired presentation timestamp given with every frame, and its actual presentation time, as well as making sure that as long as the deviation in timestamps is within given limits, no frame will be dropped or doubled when sent out via the output port. In case of a real-time stream, the method should also contributes to a minimal latency for the end-to-end solution.
There are no similar control mechanisms as described above that are implemented in software. Hardware implementations such as illustrated in FIG. 2 receive a genlock signal through a distribution method separate from the media distribution mechanism, which makes this technique unsuitable for long-distance distribution, or when using existing networks which may be bandwidth or reliability limited.
The disclosed invention requires no hardware genlock signal distribution network, and allows frame-accurate, low latency distribution of video over sub-optimal networks. In addition, the disclosed invention allows for lower cost solutions (no need to implement a gen-lock distribution network, no need to upgrade existing networks to avoid any errors), over greater distances (where genlock networks are impractical), and simplifies the installation.
This application is related to U.S. application Ser. No. 14/837,321, entitled: A METHOD FOR VIDEO SYNCHRONIZATION IN VIDEO DISTRIBUTION SYSTEMS, filed 27 Aug. 2015, which is incorporated by reference for all purposes into this specification.